Pygas, also known as pyrolysis gas, can be formed in the cracking furnaces of various refinery processes. Pygas can include alkanes, alkenes, alkynes, aromatics, naphthenes, alkyl aromatics and/or polyaromatics. After being formed in the cracking furnaces, pygas can be distilled through one or more fractional distillation columns to remove lighter hydrocarbons.
One potentially valuable component of pygas is dicylcopentadiene. Dicyclopentadiene can be formed by the thermal dimerization of cyclopentadiene in pygas. Thermal dimerization of cyclopentadiene to dicyclopentadiene can occur as the lighter hydrocarbons are distilled from pygas. However, because pygas components can have similar vapor pressures, i.e., low relative volatilities, it can be difficult to remove dicyclopentadiene from the heavier hydrocarbons in pygas by distillation alone. As a result, dicyclopentadiene can be used as fuel, e.g., for boilers and furnaces, along with heavier hydrocarbons. However, it can be more desirable to recover purified dicyclopentadiene from pygas.
Certain methods of recovering dicyclopentadiene from pygas are known in the art. For example, U.S. Pat. No. 6,737,557 discloses a method for recovering dicyclopentadiene from a hydrocarbon feedstock using two distillation columns. U.S. Patent Publication No. 2014/0364665 discloses a system including a distillation column and at least two dimerization reactors. U.S. Pat. No. 3,719,718 discloses a process that includes monomerizing dicyclopentadiene to form cyclopentadiene. U.S. Pat. No. 3,676,509 discloses a method for recovering dicyclopentadiene from a hydrocarbon feedstock by monomerizing dicyclopentadiene at temperatures from about 350° C. to about 420° C. International Patent Publication No. WO2002/036529 discloses a process for purifying dicyclopentadiene from a C5 fraction which includes the conversion of cyclopentadiene to dicyclopentadiene prior to separating dicyclopentadiene from the C5 fraction.
Japanese Patent No. 62000889B2 discloses the production of cyclopentadiene through the pyrolysis of dicyclopentadiene. U.S. Pat. No. 3,544,644 discloses liquid phase cracking of dicyclopentadiene to form cyclopentadiene. U.S. Pat. No. 5,877,366 discloses cracking dicyclopentadiene using a heat transfer fluid to form cyclopentadiene vapor. U.S. Patent Publication No. 2008/0097132 discloses a process of forming cyclopentadiene from cyclopentenes, including dicyclopentadiene, by heating the cyclopentenes in a vaporization zone prior to transfer to a cracking zone.
However, there remains a need for improved techniques for recovering dicyclopentadiene from pygas.